Various portable electronic devices have been provided. One example of those portable electronic devices is a cellular phone. While a variety of functions are provided for a cellular phone, case designs of cellular phones, display images on a display unit, melodies for notification of an incoming call, and the like are diversified according to users' preference. As one of measures to meet those demands for diversification, provision of a backlight function to a key operation unit has been proposed in order to prevent an error of key operation in a cellular phone or to prepare for use in the darkness at night or the like (for example, Patent Document 1).
To put it briefly, this proposal relates to a key backlight control method of a portable electronic device, such as a cellular phone, and intends to enable a plurality of keys of a key operation unit to emit light in different light emission colors with different luminance and light emission patterns so as to improve the efficiency of key identification and key operation when key backlights are turned on.
Patent Document 1: Japanese laid-open patent publication No. 2005-134998